Research on nutrition and health is like gathering intelligence: never perfect, rarely linear, but always useful and always suggestive. As with any carefully gathered and well-researched data, the more we have the better we can fill in the blanks and connect the dots. And the more certain we can feel about the picture that emerges, the conclusions we reach and the recommendations we make. The fascination with comparing low-carb and low-fat diet continues unabated; the latest news comes from a study published in the Annals of Internal Medicine1 released on Monday, which found that people on both types of diets lost about the same amount of weight over a period of two years. However, the individuals in the low-carb group had an edge on two fronts: their HDL (“good”) cholesterol rose more and their diastolic blood pressure dropped more.
Funded by the National Institutes of health and authored by Gary Foster, director of the Center for Obesity Research and Education at Temple University in Philadelphia, and others, the study followed 307 participants. One-hundred-fifty-three people were randomly assigned to a low-carb diet, and the other 154 to a low-fat diet. The low-carb group limited its carbohydrate intake to 20 grams per day for the first 12 weeks, and then gradually increased its intake of fruits, vegetables, whole grains and dairy foods until individuals reached their desired weight. There were no calorie or fat restrictions. The low-fat group consumed 1,200–1,500 a day and kept fat to 30 percent of their diet.
How Research Works
Though everyone would love to see that one, ultimate “heavyweight match,” which pits low-carb diets against high-carb diets and gives us a winner with an undisputed knockout, the research world just doesn’t operate like that. It never seems to cooperate with our human need to fit its complexities into a nice, neat box wrapped in a 60-second sound bite for the evening news. Instead, research inches along with small studies on specific populations, usually for a much shorter time than we would like—for reasons of cost and practicality—and delivers specific measurements. It’s then up to health professionals to look at, evaluate and draw conclusions based on the findings.
Most of the conventional medical opinion, meaning those who assume that low-carb diets increase the risk for heart disease by raising cholesterol, is based on the simple and unsupported theory that “you are what you eat.” Now that’s all changing.
And the news is very good indeed.
Many Studies Investigating Many Things
In the last few years peer-reviewed journals have published more than 50 studies or review papers investigating low-carb diets. Some focused mainly on the effect on weight loss. Others were interested in the effects on blood lipid levels such as total cholesterol, LDL (“bad”) cholesterol, HDL (“good”) cholesterol and triglycerides (a kind of fat in the blood that increases risk for heart disease). Still others looked at measures of inflammation, which is now understood to also be a risk factor for heart disease. And a few looked at the effect of low-carb diets on medication dosages, particularly in type 2 diabetics, as well as measures of diabetic risk such as fasting insulin and a special type of sticky protein called hemoglobin A1c. (A reading of over 6 on this measure is nearly always an indicator of diabetic complications to come.)
Some of the studies used only men; some used women; some used both. Some used only obese subjects; some used normal-weight subjects; some used primarily diabetics. Yet the picture that is beginning to emerge is much clearer than you might imagine, and certainly more nuanced and evolved than the one we had a mere three or four years ago. And if you are one of the many thousands of people successfully following the Atkins Diet, you now have a lots more hard facts with which to counter many of the outdated misconceptions.
A Snapshot of the Big Picture
A good place to start to look at the big picture is a review paper by Jeff S. Volek, Ph.D., and Eric C. Westman, M.D.2These two respected researchers and two of the authors of The New Atkins for a New You decided to take a look at the published research and present an overview of the trends and results they found, much as we’re doing here. Their first finding: with only one exception, studies that compared low-carb to low-fat diets of the same number of calories showed that the low-carbers lost more weight. (In the single exception all the study subjects were morbidly obese and consumed only 600 calories, which is an absurdly low number.)
The review article also points out that the studies that actually assessed body composition on a very-low-carb diet suggested that there was a tendency to preserve lean body mass and to lose fat mass. This happened even when there were no changes in physical activity! This finding is important because muscle burns more calories than fat, so to the extent that you lose fat and keep (or gain) muscle, you are actually raising your metabolic rate, making your body into a “better butter burner.”
Drs. Volek and Westman also found that contrary to popular myth, the Atkins Diet does not increase the risk for cardiovascular disease, as confirmed by this most recent paper by Foster et al. The authors of The New Atkins for a New You, who have themselves done a fair amount of original research, assert that low-carb diets may actually improve the cardiovascular risk profile in some individuals, even without weight loss. They also point out that the most dramatic and consistent response to the diet is a moderate to large decrease in fasting triglycerides as well as postprandial (after a meal) triglycerides, both of which are important independent risk factors for cardiovascular disease.
Two Possible Results, Both Good
My own review of the literature shows two possible weight-loss outcomes when low-carb diets are compared to low-fat ones. Usually the low-carb diet produces more weight loss than the low-fat or low-calorie diet; once in a while it produces the same amount of weight loss. Never does the low-carb diet produce less weight loss than the “conventional” diet it is being compared to. And as we will see, even when weight loss is comparable, the low-carb diet nearly always outperforms the low-fat diet in the blood lipid department.
Are you beginning to see a picture emerging? If one diet almost always produces a better cardiovascular risk profile than the other, and, in addition, usually produces more weight loss, why on earth would you not choose that program for your weight loss strategy?
Finally, the Westman and Volek review article points out that the overall data from very-low-carb diets actually show a potentially favorable effect on both the risk of developing type 2 diabetes and insulin resistance.
The Complexities of Cholesterol
One particular measure that a number of studies examined is of particular interest, since it is only now beginning to get the attention it deserves. We now know that cholesterol is much more complicated than just the “good” (HDL) and the “bad” (LDL). There is also “the ugly.” We now know that LDL itself comes in a couple of different “flavors”—we call them particle sizes, and they behave quite differently in the body. The small, dense particles (pattern B) are quite dangerous and atherogenic, meaning they block arteries—these are “the ugly.” It’s these particles that can wedge between existing cholesterol plaques and your artery wall where they tend to oxidize and cause all the problems attributed to “bad” cholesterol. However, the large, fluffy LDL molecules (pattern A) are “too fat” to wedge themselves between plaques and artery walls and are therefore more benign. So in recent years, research has begun to explore changes in particle size as a result of diet. And guess what? Study after study has shown a trend towards the better (pattern A) particle size as a response to a low-carb diet.
Inflammation, the New Kid on the Block
And then there’s inflammation, the new superstar of blood tests. Important enough to rate a cover story in Time, entitled “Inflammation: The Silent Killer,” inflammatory markers are excellent predictors for heart disease. The two markers usually measured are C-reactive protein, which is made by the liver in response to inflammation, and serum amyloid A (SAA). Two studies by K.D. O’Brien3,4 examined how these markers were altered in response to a low-carb diet. In one study, he compared two 1,200-calorie diets, one an Atkins Induction plan and the other a standard low-fat, low-calorie plan. Both diets had favorable effects with respect to weight loss, blood pressure and lipids. But the low-carb diet outperformed the low-fat diet in every parameter.
The Atkins Induction diet resulted in:
1)greater weight loss,
2)greater reductions in triglycerides,
3)lower SAA and
4)a non-significant trend towards lower CRP.
O’Brien reported, “The findings were surprising because they were completely the opposite of what we expected to find. We were absolutely convinced that we would find some parameter that showed a disadvantage of the low-carbohydrate diet compared to the low fat. Of all the parameters we looked at we could not find a single one that showed the low-fat diet was superior”.
So what can we conclude? Certainly, to quote an old saw, “more research is needed.” In fact, more research would be welcomed! But we now have enough available good research to draw certain conclusions:
1)Low carbohydrate diets do not adversely affect cardiovascular risk profiles. You are not going to get heart disease from following a low-carb diet, even one that is high in natural fats, although you should stay away from foods containing trans fats synthesized by food manufacturers. In fact, your cardiovascular risk profile stands a very good chance of improving. LDL cholesterol particle size tends to change for the better, HDL size and amount tends to go up and triglycerides almost always come down. In fact, such HDL and triglyceride changes from a low-carb diet occurred in one study5 to such an extent that they were similar to commonly used cholesterol-reducing drugs derived from fibric acid and niacin! Imagine a diet that has the health benefits of a drug without its normal laundry list of side effects (not to mention high prices).
2)Low carbohydrate diets seldom result in less weight loss than an equal-calorie low-fat diet. Although once in a while they “tie” on the weight-loss scale, most of the time they produce greater weight loss than their counterparts. And they appear to be a lot easier to stay on, largely because the satiating nature of fat and protein reduce hunger.
3)Inflammatory markers seem to improve on low-carb diets. Undoubtedly this will be a fertile area of new research in years to come, but right now it sure looks good.
4)Diabetic indicators like A1c and glucose control and insulin sensitivity almost always improve. In some studies medication use either dropped or was halved.
All in all, the results are great news for followers of the Atkins Diet. I am confident that there is a lot more good news to come as this wonderful approach to a healthy life continues to attract devotees and increasingly gets the serious—and long-overdue—attention from the research community. Our website will continue to make available all the latest research so that you can read it for yourself and share it with your doctor. All the studies mentioned in this article are referenced below.
So enjoy that chicken leg, surround it with plenty of buttered vegetables and a green salad dressed with olive oil, take your omega-3 oils and eat your way to a healthy weight and a wonderful life!
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1)Volek, J.S., and Westman, E.C., “Very-Low-Carbohydrate Weight-Loss Diets Revisited,” Cleveland Clinic Journal of Medicine, Vol 69, Number 11, Nov 2002.
2)Foster, G., et al., “Comparison of Weight Loss at 2 Years on a Low-Carbohydrate Versus Low-Fat Diet,” Annals of Internal Medicine, August 3, 2010 153:I-35.
3)O’Brien, K.D., Brehm, B.J., et al., “Greater Reduction in Inflammatory Markers With a Low Carbohydrate Diet than with a Calorically Matched Low Fat Diet,” Presented at American Heart Association’s Scientific Sessions 2002 on Tues, Nov 19, 2002, Abstract ID: 117597.
4)O'Brien K.D., Brehm, B.J., Seeley, R.J., et al., "Diet-Induced Weight Loss Is Associated with Decreases in Plasma Serum Amyloid A and C-Reactive Protein Independent of Dietary Macronutrient Composition in Obese Subjects,”Journal of Clinical Endocrinology & Metabolism, 2005; 90:2244-2249.
5)Hays, J.H., DiSabatino, A., Gorman, R.T., et al., “Effect of a High Saturated Fat and No-Starch Diet on Serum Lipid Subfractions in Patients with Documented Atherosclerotic Cardiovascular Disease,” Mayo Clinic Proceedings, 78(11), 2003, pages 1331-1336.